Das, Subrata Kumar

Abstract [en]

Abstract Synthetic Aperture Radar (SAR) is an important tool for remote sensing now a day. SAR image quality measurements play an important role in the development of SAR image digital processing methods. The essential SAR image quality assessments are spatial resolutions, Integrated Sidelobe Ratio (ISLR) and Peak Sidelobe Ratio (PSLR). This thesis mainly focuses on the UWB SAR image quality measurements. Since the spatial resolutions depend on integration angle in UWB SAR, measurements should be performed at different integration angles for a UWB SAR system. Evaluation or comparison of the resolutions obtained with different UWB SAR systems can be based on another measurement named differential resolution measurements. For ISLR and PSLR measurements, it is seen that elliptical areas are more suitable for delimitation of mainlobe and sidelobe areas of a UWB SAR image than rectangular areas. This is proved by an investigation relied on a newly derived Impulse Response Function in SAR Imaging (IRF-SAR) instead of the widely used sinc function. From this investigation, we can also see that a factor of 2.5 is sufficient to represent the spread of mainlobe in both azimuth and range direction. In this work, we use simulated UWB-low frequency CARABAS-II data. The simulations are performed in Matlab. In spite of the main drawback in computational cost, Global Backprojection (GBP) algorithm is still selected for UWB SAR image formation due to its time-domain characteristics such as extreme range migration handling, manageable motion compensation.